Based on the significant findings of the preliminary study conducted by the investigators, a three year research program is proposed to study three-dimensional kinematics involving range and pattern of motion of segments obtained from 30 fresh cadaver lumbar spine specimens. The objective of the proposed research will be met by conducting in vitro experiments using the test facilities and instrumentations, specially designed, developed and tested for this purpose. In addition to the traditional modes (Flexion/Extension, Lateral bending and Axial rotation), three dimensional motion of the lumbar spine will be studied in ten other loading planes (15 degrees apart) that lie in between sagittal and frontal planes. All modes of motion of the lumbar segments will be studied, with and without compressive preload, for the independently and incrementally applied moment loads and shear loads. The kinematic data will be obtained under four conditions: (1) intact motion segment, (2) motion segments with posterior elements transected, (3) motion segments with transected posterior half of the intervertebral disc, and (4) motion segments with transected anterior half of the intervertebral disc. The three-dimensional kinematic characteristics of the lumbar motion segments will be studied in terms of the following kinematic parameters: (1) range of motion in each plane of loading in terms of total rotation and translation about and parallel to the screw axis, and their motion components along the three mutually perpendicular axes of a reference system, (2) parameters of the screw axis in terms of direction cosines and coordinates of the point of intersection of the screw with a prescribed plane. A total of 30 lumbar spine cadaver specimens will be tested. The data collected from the motion segments of these specimens will be analyzed statistically to test the differences in means of kinematic parameters of the intervertebral motion. The significant contribution of the proposed research will be to provide the signature data or description of the 3-D kinematics of vertebral motion and its normal variation in a quantitative form for each level of the intact and transected motion-segments of the human lumbar spine.